1. Field of the Invention
The present invention relates to a highly adhesive pressure sensitive adhesive composition which mainly contains an acrylic polymer and is used in labels, pressure sensitive adhesive tapes or sheets, as well as to such a highly adhesive pressure sensitive adhesive sheet using the highly adhesive pressure sensitive adhesive composition.
2. Description of the Related Art
Conventional pressure sensitive adhesive compositions, pressure sensitive adhesive tapes and sheets can adhere to adherends at atmospheric temperatures at a certain pressure of finger-pressure and are widely used for bonding, packaging, surface protecting or for electrical uses. Specifically in bonding applications, demands have been often made on highly adhesive pressure sensitive materials in order to ensure high reliability and safety.
When members bonded using, for example, such pressure sensitive adhesive tapes become unnecessary, the members themselves including the pressure sensitive adhesive tapes as intact are discarded or are disposed by incineration. However, demands to recycle recyclable materials such as aluminium, poly(ethylene terephthalate), polystyrenes and other plastics have increased from the viewpoint of ecology. Upon recycling, different materials constituting the members must definitely be separated and the pressure sensitive adhesive tapes must be peeled off from the members.
However, conventional pressure sensitive adhesive tapes, especially highly adhesive pressure sensitive adhesive tapes, often increase in their adhesive strength due to changes with time after adhesion to adherends, and cannot significantly be peeled off from the adherends after adhesion or leave the pressure sensitive adhesives as deposits.
As is described above, conventional pressure sensitive adhesives, especially highly adhesive pressure sensitive adhesives for use in recycle members, become more highly adhesive with their increasing tackiness (adhesive strength) with time and thereby cannot significantly be peeled off from the adherends or stain the adherends. For example, the pressure sensitive adhesives cause adhesive deposits on the adherends. Demands have therefore been made to solve these problems.